This variable oscillator with power step for alarms was found in an American documentation from the 90's. The power transistor must be equipped with a heat sink.
This circuit is from a Radio Electronics from October 1963. The LDR and transistors are from the...
This circuit was found in an American documentation from the 80's. The transistor is a...
This circuit, found in documentation from the 1980s, uses an operational amplifier from that time....